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Does anyone here work on plasma displays?

A friend of a friend got a "deal" and a faulty Benq 46W1 plasma display and I've been asked to fix it. I know nothing about plasmas. So far I've had a quick look at the image on screen and it's not looking promising.

There is section of the screen extending in approximately 4 inches from the left side that is completely dead. The edge of the dead area is an irregular shape, not a straight line of pixels. Approximately 4 inches in from the right side there is a blue vertical line 1 or 2 pixels wide. The Benq logo is burnt into the center of the screen. There are random flickering red pixels visible against the black background with no source connected. When a source is connected a red snow takes over most of the image (other than the dead section).

I'm guessing that that short of replacing the panel there is nothing that can be done about the dead section, blue line and screen burn. If the red snow can be dealt there may be enough screen area left for a 4:3 image which is better than nothing.

Any suggestions?

Should I build the world's first plasma fish tank? :)

The biggest service issue I hear about with all flat panel TVs is parts availability. Can you get parts for this set? I've never even heard of that brand. I don't really know anything about plasma sets either but it sounds like the display or its driver circuitry is bad. Has the set been dropped or suffered other impact damage? You should probably replace it with a tube type color console.

Plasmas would probably make a better ant farm than a fish tank. :scratch2:

99% of the time from what I have heard a bad display is unrepairable.

Bet it was dropped or whacked on that side. From some of what I hear, these things make CRTs look like bridge abutments, they're so blasted fragile. But they're BETTER, doncha know...Grrrrrrrrr....

It could be louse soldering connections or bad caps, I hear those plasma sets get really hot, but I'm not sure where you should start looking...

You should probably replace it with a tube type color console.
:lmao: I like this suggestion here. These old sets will probably outlast the sets they're making today anyway.

Well, hell, they DO have a 40, 45 year head start on 'em...(grin)

With the burnt logo on the screen, it is not worth repairing. That cannot be fixed (other than replacing the panel, which would cost more than a new plasma TV, and an LCD would be a better buy), so the rest is not worth troubleshooting. If you want to just try things, see if you can get a service manual from Benq for it. I have not yet done any plasma or LCD repairs, but I expect/hope to start learning on-the-job soon enough.

A bit of googling suggests that red (or green) snow isn't an uncommon fault with plasmas, especially various Philips/LG models. A couple of sites do say which board needs to be replaced in various models, but they don't actually say what is wrong with the board. I guess they aren't repairable at the component level.

I will probably have a closer look at it if for no other reason than I haven't seen inside a plasma yet. I won't be spending any real time or money on a lost cause though.

Is anyone interested in pictures of a plasma disassembly?

...

Broken plasmas can go for several hundred on ebay.

They say a fool is born every minute :nono:

Charles

Is anyone interested in pictures of a plasma disassembly?
Yes, I would like to hear about (and see) your experiences if you do pull it apart and/or try some repairs.

Now, why would anyone pay several hundred $$ for a broken Plasma TV? Are these buyers unaware that it will cost more to repair than what a new set would cost? Heck, someone would about have to PAY ME to haul one off! Several hundred $$ will buy me a great deal of vintage stuff!

Answer: someone who needs a powersupply, an outer plastic frame, rear case, feet etc would pay decent money for it on ebay. Never forget the person who needs a dead one to fix his own.

. Never forget the person who needs a dead one to fix his own.

Quite true.

I've more then once brought something back to life using "cadavers" from other dead electronics.

I work part time in a TV shop in Miami Fl. that has been in business since 1953. People still bring in their beloved electronics from the 1950's thru 1970's and when one or two come in I get called to repair them. They are also the authorized service center for companys the build/sell plasma, LCD, and DLP sets. What I have seen that if the problem cannot be corrected by software upgrades, (quite a few can ) or the replacement of large circuit boards the manfacturer says to tell the customer that the device is not economicilly repairable. If under warranty the bad section is replaced, they usually ship second day air. There are a lot of folks with 5 year old plasma sets who are very unhappy after pitching their 15 year old still working CRT rear projection sets to make room for the new flat screen technology.

It is sad that these companies are not even trying to support component-level repairs. I doubt that most of the repairs needed are the complex chips; most surface-mount repairs I have done were caps or transistors, and flat-panel TVs could be the same. I understand not repairing a 19" CRT TV, but a flat panel that cost $3000 new should be worth more effort than that.

It is sad that these companies are not even trying to support component-level repairs. I doubt that most of the repairs needed are the complex chips; most surface-mount repairs I have done were caps or transistors, and flat-panel TVs could be the same. I understand not repairing a 19" CRT TV, but a flat panel that cost $3000 new should be worth more effort than that.

I forgot to mention that the manufacturer wants the old board back or a very expensive core charge. There is also a note in the box that the replacement board comes in that says something like, This board my have been refurbished but meets all the specs and warranty as does a new one.

...

Wonder if PTS electronics rebuilds plasma and LCD modules, they've been in the panel/tuner rebuilding business for years.

I forgot to mention that the manufacturer wants the old board back or a very expensive core charge. There is also a note in the box that the replacement board comes in that says something like, This board my have been refurbished but meets all the specs and warranty as does a new one.
This idea is not bad, provided the "exchange" cost is reasonable. Also, since they have these exchange programs, clearly someone is doing component-level repairs on plasma/LCD circuits. If they refuse to make service information available, I wonder if the FTC could get involved for some kind of business-restraint issue?

Answer: someone who needs a powersupply, an outer plastic frame, rear case, feet etc would pay decent money for it on ebay. Never forget the person who needs a dead one to fix his own.

I understand that; but, it would be just my luck that the same part I needed would be bad in the busted plasma I just paid $500 for. The only way I'd consider paying any large amount of $$ for anything broke would be if I knew for certain that it had a good part for something else I needed. It will be interesting to see what new plasma sets sell for in 10-15 years. I wonder if they will ever be as cheap as most current CRT sets are.

With modern electronics, the extremely complex integrated circuits and the surface mount technology(not to mention the lead-free soldier that is coming) is making board repair at the local TV shop very difficult. At the manufacturers location, special test fixtures(such as bed of nails, special test equipment to exercise the ICs test modes, etc) would make more economic sense than at an individuals TV shop. This would also be true of the specialized equipment needed to reliably replace surface mount components.

This is my opinion as to why board replacement, not repair is being done at most electronic service locations today. (It is also the reason that I try to avoid working on any electronic equipment made after about 1985-not only are the components easier to replace-they are easier to find and purchase, including vaccum tubes.)

It will be interesting to see what new plasma sets sell for in 10-15 years. I wonder if they will ever be as cheap as most current CRT sets are.
Plasma displays will probably not be made for more than about another five years, as LCD displays get better and better. LCD TVs in five years will cost about the same as comparable-sized CRT TVs cost recently, that is, US$100 for a 15" and maybe $150 for a 19-inch. Actually, I would expect those prices to be hit in about two years, not five. $500 or less will buy you a 40-42" LCD within five years (or maybe two years), $1000 for a 52". Eventually, the 42" will be $300 and the 52" will be $500, probably. Projection sets will go away within five years as well, when the really big LCDs (65-80") start to sell for less than US$2000.

It was only four and a half years ago that 42" non-high-definition plasma displays went down to US$3000-3500, and now the near-high-def ones are under $1000. A 37-inch LCD in Japan cost the equivalent of $7500 in January 2003, and I have seen that size recently for well under $1000.

Wonder if PTS electronics rebuilds plasma and LCD modules, they've been in the panel/tuner rebuilding business for years.

Some, YES. My friend in West Los Angeles uses them often for plasma and LCD boards. However, the reason that a lot of those boards are not component level repairable is that they're multi-layer, and contain BGA comonents. (BGA= Ball-Grid array, which cannot be soldered with an iron. It takes a special BGA placement heat projector and X-ray viewer.)

I've used PTS for many boards too. I trust their work 90%, but not on anything from a CRT projection Phillips. They've done several Pioneer CRT projection boards for me, and also a few Sony XBR CRT boards that had really weird and hard-to-troubleshoot problems.

Charles

...

BGA is the worst thing to happen to the electronic hobby. Even dense surface mount can be done at home, but BGA is virtually impossible. Even if it works, you have no way to inspect your soldering to make sure it's good. I've started to see a lot of laptops and video cards with bad BGA soldering. Certain models have very high failure rates.

I had some exposure to it while I was working in the test lab at a local PC board mfg company. I never operated the BGA bench, but I did fill in on the BGA X-ray for the X-ray tech once in awhile (I had to get X-ray certified and wear a badge that was supposed to explode in my face or something, to warn of X-ray exposure in case of a leak :yes: )... Basically, the X-ray shows the density of the balls. If there are white dots, or if they're not circular, the BGA connection is a fail. With no X-ray, it's 100% impossible to see what you have.

Charles

The screen burn-in is apparently not fixable. You might get lucky and open her up and look on the boards and find something obvious like a leaking capacitor. I've fixed LCD monitors this way, not knowing a thing about how to actually fix one.

This is the first time I've heard of BGA. (well, I don't get out much...) Would be interesting to see just what it looks like. Is it fairly universal now?

...

BGA is not a problem for us, after all, most of our gear is vintage and the most you will find that is hard/impossible to fix is the 'printed' resistors that kenwood used in the 1970's or the sanken darlington packs that are unobtania, along with some wierd FETs, strange pallet output transistors and particularly oddball value large power supply caps. BGA is the provence of modern gear and it has no place in real hifi. As an example, when Sony ES went from all through hole to a mix of surface and through hole- the quality was gone. You can't put surface mount componentry in a power amp driver stage and not expect the things to blow up like fireworks. I know a certain 5 channel 25kg gold power amp from Sony that appears on eBay all the time where the driver transistors are tiny crumb sized surface mounts- what a joke. All this BS about shorter signal paths etc etc for a preamp, poweramp and reliability is complete rubbish. We all know through hole has the runs on the board in high current hifi applications. My policy is to not have any real hifi with surface mount in it. My CD players cross the line a little due to the odd surface mount IC, but basically after 1990/1 they all turned to crap in terms of construction. You can't have a dvd player without surface mount somewhere, but that's life i guess, no one uses one for serious hifi anyway.
The following rules will help you sort out real hifi from junk:
The output transistors are discrete and the more the better.
The power supply caps have a recognized brand on them and the larger value the better. (no flying pigeon brand or sun-moon brand etc etc)
The power amp stage has no ICs in the signal path.
The amp is heavy and solid.
It has a speaker A+B switch where they can run in parallel.
It has two phono inputs or a MM/MC input.
An integrated amp without a phono input is modern JUNK.
A tuner should weigh more than a bottle of milk.
The more heads and motors in a cassette deck, the better it is.
And my personal favourite which I apply to CD players. If you can't lift the machine up by the the CD drawer- it IS a piece of junk. (that means as a minimum, lift the machine off the shelf by the end of the drawer up to at least 45 degrees). The old machines can do it easily. A CDP101 can be held by the drawer. Early philips/marantzs can, as can most of the sony ES line, some denons and pioneers and others. I dare you to try it with some of these 'audiophile' machines that are held together with plastic clips- haha.
Anyway, enough ranting...
john

Bryan-

Look it up on Wikipedia. I wasn't familiar with it either, but after I read their article, I realized I have seen some boards with parts like that, particularly computer components.

Edit: Oops, I didn't see there was a third page and Andy already mentioned it.

You should probably replace it with a tube type color console.

God, I love that... it sounds so genuine. :)

I want to see pix of the innards!

Pictures will be posted when I get back there to work on it. I didn't bring it home with me (trying to man handle it around by myself is probably a guarantee that I would crack the panel).

http://65c02.org/images/ak/benqplasma1.jpg

The view after removing the 30 or so screws holding it together. It was manufactured in 2002. Judging by stripped screws posts and the texta marks on almost every board it has been repaired several times in it's 5 year life.

The small board at the top of the picture is carries the standby power supply and the audio amplifier.

The panel itself is made by Chungwhua. Most of the other components are known brands (Rubycon capacitors, etc). That kind of surprised me at first considering the kinds of off brand and left over parts I'm used to seeing in a lot of recent cheap electronics, but I guess that can't get away with the kind of shorts cuts I see in cheap CRT TVs/DVD players/etc here.

http://65c02.org/images/ak/benqplasma2.jpg


The signal board which provides VGA and DVI inputs and the daughter card which adds composite and component video inputs. The only BGA IC in the unit is on this card. There is a space and connector for another card, probably a TV tuner.

http://65c02.org/images/ak/benqplasma3.jpg

The X scanning board. It's mainly through hole components and loads of surface mount diodes. Some of the diodes have already been replaced in a previous repair.

http://65c02.org/images/ak/benqplasma4.jpg

The Y scanning board. More of the same. No visible repairs on this board.

http://65c02.org/images/ak/benqplasma5.jpg

The driver (?) board. A stack of FPGAs, buffers and some RAM. I'm guessing that in a brand name display they'd probably use some custom ICs here. One of the surface mount capacitors had already been replaced with a through hole part.

http://65c02.org/images/ak/benqplasma6.jpg

The power largely obscured by it's heat sink. This is all through hole bar one tiny module. I found 2 bad capacitors (1500uF/200V) here that appear to be filtering the 175VDC rail that drives the panel. I don't know if this is the cause of the red snow yet, I don't have any suitable replacements on hand. I have seen bad filter capacitors that measured okay cause snow in CRT sets before.

All in all it looks like plasmas are more repairable than I thought, though this may not apply to other brands/models. I'm going to replace the bad capacitors to see if the picture improves, but considering the damaged panel I won't be spending any more time/money on it otherwise. If the panel was okay I'd look into it further. If I knew exactly what I was looking at I could handle working on the power supply and scan boards. Someone with greater skill and a finer soldering iron than I have could work on the driver and signal boards (with the exception of the lone BGA IC).

Maybe someday I'll understand half of what you just said.
Great pics!:thmbsp:

Nice pictures and description, dr. ido. I hope you have success with the capacitors, if only as a learning experience.